p trap lower than drain pipe

How Far Below Drain Pipe Can P-Trap Be?

In most cases when you are remodeling your kitchen or vanity and you get a deeper sink.The plumbing is likely not to line up, the p trap ends up lower than the drain pipe, because the sink pushes it down several inches.

However, the p trap should not be lower than the drain pipe because in such a case, gravity will have to force the water out rather than letting it flow downwards naturally.

In this article we will discuss how far below the drain pipe a p trap can be and what you can do when the p trap doesn’t line up.

How Far Below Drain Pipe Can P-Trap Be?

The maximum distance a p trap can be from the drain pipe is 24 inches as required by the international plumbing code. There is however, no minimum distance stated but this will highly depend on the height of the drain pipe from the wall.

What To do When P Trap Doesn’t Line Up with Drain

If you are installing a new vanity and you find that the p trap does not line up with the drain which happens often. 

The horizontal distance changes will limit the reach of your p trap. And unfortunately you cannot find more horizontal p traps.

Because our drain coming out from the wall and sink drain aren’t lined up we will need to use a 45 degree elbow fitting to divert the drain angle towards the sink drain.

  • Install a 1 ½ inch pipe from the drain on the wall/ builder. 
  • Then install a 45 degree elbow to change the direction of the drain from the wall. 
  • Use a measuring tape to measure the length of the pipe that will fit between the p trap and the 45 degree elbow 
  • Now cut the piece you just measured.
  • Put the trap adapter onto the piece you just cut.
  • Now slide the p trap onto the tail piece from the sink / dry fit the p trap on the drain.
  • Finally align the p trap with the pipe from the 45 degree elbow from the drain.If everything aligns , put a primer and cement everything up and then tighten up.
  • Lastly, test for leaks by running the faucet.

See also How Deep can A P trap be?

How To Raise P Trap in Bathroom Sink

With so many types of vanities available in the market today, there’s excitement with installing a new vanity in your home. However, you may run into plumbing problems, like the p trap being too low for the vanity. 

On that note, how do you fix the problem if the p trap is too low for vanity? Here are some great options:

  • Cut the vanity drawer to allow the p-trap to occupy the space beneath.
  • Add an extension tailpiece to the drain to bring the p-trap outlet to the same level as the drain pipe.
  • Elevate the trap arm- keep in mind that this solution involves opening the wall to access the drain pipe. 
  • If you don’t want to make any adjustments to your plumbing system, you can buy a new vanity. One that won’t get in the way of the p-trap.

Do P-traps Need To Be Vented?

Whether in the kitchen, bathroom, or other areas, all sinks need sink vents to function correctly. While a p-trap keeps sewer gasses from your home, a vent prevents water from being siphoned out of the p-trap.

Moreover, venting prevents pressure buildup in the sewer lines by giving the sewer gasses an area to vent. Without a sink vent, the back pressure created when water empties from the drain pipe, dragging wastewater out of your sink p-trap can make sewer gasses enter your home.

Sinks need vents since the pressure exerted on the drain pipes during water drainage has to balance. You have probably heard the “glug glug” sound at some point when using the drain in commercial buildings, older cabins, and homes. 

This is the sound of air and sewer gasses being pulled or pushed through the p-trap. While you may not consider this a big deal, it will eventually slow down the water seal if not fixed, stopping the sink p-trap from safeguarding your building or home against sewer gasses. 

See also How Low Can a P trap go?

FAQs on P Trap Lower than Drain Pipe

Does P Trap Height Matter?

The p trap height does matter because if it is too shallow then the water in the trap can easily evaporate taking away the seal that prevents sewer gases from coming up. If it is too deep then the water will flow in too fast and hence leave behind sludge. That is why the recommended p trap height is between 2 inches and 4 inches.

Does Vent Need To Be Higher than P Trap

The vent needs to be higher than than the p trap so that it can be able to maintain the pressures on both sides of the trap and prevent siphoning back of water on the p trap and air.

See Also Can A P Trap Go Either Way

Can P Trap Turn 90 Degrees

A p trap cannot turn 90 degrees because the trap arm is not allowed to make a cumulative change of more than 135 degrees. In this case for a p trap to turn 90 degrees it will make a cumulative change of 180 degrees which is not allowed

Conclusion

A p-trap can only be effective if properly installed; therefore, you must ensure it doesn’t sit lower than the drain pipe. If the drain and the p trap do not align then you can use a 45 degree elbow to divert the direction of the drain towards the p trap to make sure they align properly.

See also Can P Trap Be Higher than Drain Pipe

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